Detailed explanation of the use of vue crop preview component

This time I will bring you a detailed explanation of the use of the vue cropping preview component. What are the precautions for the vue cropping preview component? The following is a practical case, let's take a look.

Vue version cropping tool, including preview function

Final effect: qiuyaofan.github.io/vue-crop-de…

Source code address: github.com/qiuyaofan /v…

The first step: first use vue-cli to install the scaffolding (see the vue-cli official website if you don’t know how to install it)

// 初始化vue-cli
vue init webpack my-plugin

The second step: create the file

Create new src/views/validSlideDemo.vue,

Create new VueCrop/index.js, VueCrop.vue in src/components,

configure access routes in routes/index.js (see github source code for details )

The final generated file structure is as follows:

Step 3: Register components

1. Reference all plug-ins: src/ components/index.js

// 导入插件入口文件
import VueCrop from './VueCrop/index.js'
const install = function (Vue, opts = {}) {
 /* 如果已安装就跳过 */
 if (install.installed) return
 // 注册插件
 Vue.component(VueCrop.name, VueCrop)
}
// 全局情况下注册插件
if (typeof window !== 'undefined' && window.Vue) {
 install(window.Vue)
}
export {
 install,
 // 此处是为了兼容在vue内单独引入这个插件，如果是main.js全局引入就可以去掉
 VueCrop
}

2. Globally call the plug-in: src/main.js (vue plugins official documentation explains install)

import Vue from 'vue'
import App from './App'
import router from './router'
// 新加的：导入入口文件
import { install } from 'src/components/index.js'
// 全局调用，相当于调用 `MyPlugin.install(Vue)`
Vue.use(install)
Vue.config.productionTip = false
/* eslint-disable no-new */
new Vue({
 el: '#app',
 router,
 components: { App },
 template: '<App/>'
})

3. The VueCrop entry file calls VueCrop.vue: src/ components/VueCrop/index.js

// 导入vue
import VueCrop from './VueCrop.vue'
// Vue.js 的插件应当有一个公开方法 install 。这个方法的第一个参数是 Vue 构造器
VueCrop.install = function (Vue) {
 // 注册组件
 Vue.component(VueCrop.name, VueCrop)
}
export default VueCrop

Summary: I always had a misunderstanding at the beginning, thinking that myPlugin.install is a method of vue. In fact, it is not. It is just a public method for us to construct plugin ID, which is understandable. The method of constructor in native js:

function MyPlugin(){
 console.info('构造函数')
}
MyPlugin.prototype.install=function(vue,options){
 console.info('构造器vue:'+vue);
}

and the actual registered component is: Vue.component()

So, vue The plug-in registration process is:

1. Call main.js:

import { install } from 'src/components/index.js'
vue.use(install)

2. Add the install method to index.js and call Vue.component to register the component

3. The index.js in the component is the same as the index.js of all components

Step 4: Design and develop your own components and build the component structure

Before this, you can first understand the naming of the components Specifications, etc., please refer to the article Nuggets: Vue front-endDevelopment specifications, of which point 2 is explained in detail

First, determine your own calling method and the parameters that need to be exposed

<vue-crop
:crop-url="cropUrl1"
:ratio="ratio"
:height="460"
:width="460"
:previewJson="previewJson1"
class="c-crop--preview_right"
@afterCrop="afterCrop"
>
>

Among them, @afterCrop="afterCrop" is the callback function after cropping is completed , and the others are attribute configurations

src/components/VueCrop/VueCrop.vue, you can use this.$emit('afterCrop') to trigger the afterCrop event in the demo

export default function (element, options) {
 const moveFn = function (event) {
  if (options.drag) {
   options.drag(event)
  }
 }
 // mousedown fn
 const downFn = function (event) {
  if (options.start) {
   // 调用参数中start函数
   options.start(event)
  }
 }
 // mouseup fn
 const upFn = function (event) {
  document.removeEventListener('mousemove', moveFn)
  document.removeEventListener('mouseup', upFn)
  document.onselectstart = null
  document.ondragstart = null
  if (options.end) {
   // 调用参数中end函数
   options.end(event)
  }
 }
 // 绑定事件
 element.addEventListener('mousedown', event => {
  if (options.stop && options.stop(event, element) === false) {
   return false
  }
  document.onselectstart = function () {
   return false
  }
  document.ondragstart = function () {
   return false
  }
  document.addEventListener('mousedown', downFn)
  document.addEventListener('mousemove', moveFn)
  document.addEventListener('mouseup', upFn)
 })
}

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